Systems and methods for measuring physical characteristics of semiconductor device elements using structured light

ABSTRACT

A method of determining a physical characteristic of an adhesive material on a semiconductor device element using structured light is provided. The method includes the steps of: (1) applying a structured light pattern to an adhesive material on a semiconductor device element; (2) creating an image of the structured light pattern using a camera; and (3) analyzing the image of the structured light pattern to determine a physical characteristic of the adhesive material. Additional methods and systems for determining physical characteristics of semiconductor devices and elements using structured light are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/469,830, filed Aug. 27, 2014, now U.S. Pat. No. 9,810,641 B2, whichclaims the benefit of U.S. Provisional Application No. 61/873,288, filedSep. 3, 2013, the contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to systems and methods for measuringphysical characteristics of semiconductor device elements (often inconnection with bonding operations of the semiconductor elements), andmore particularly, to improved systems and methods for measuring suchphysical characteristics using structured light.

BACKGROUND OF THE INVENTION

Semiconductor devices include various physical features orcharacteristics that are desirably controlled. For example, typically itis desirable that semiconductor dice are substantially flat prior topackaging (e.g., prior to die attach processes, thermo-compressivebonding processes, etc.). Also, it is typical that certain physicalattributes of elements included in a semiconductor device or package bemeasured to ensure conformity with design criteria or specifications.

Specifically, in thermo-compression bonding (e.g., bonding asemiconductor device to another semiconductor device with copper pillarsor similar conductive structures between the devices), physical featuresor characteristics of the bonding elements are desirably controlled.This is particularly true in simultaneous thermo-compression bonding ofmany devices.

Thus, it would be desirable to provide improved systems for, and methodsof, measuring and/or controlling such physical characteristics.

SUMMARY OF THE INVENTION

According to an exemplary embodiment of the present invention, a methodof determining a physical characteristic of an adhesive material on asemiconductor device element using structured light is provided. Themethod includes the steps of: (1) applying a structured light pattern toan adhesive material on a semiconductor device element; (2) creating animage of the structured light pattern using a camera; and (3) analyzingthe image of the structured light pattern to determine a physicalcharacteristic of the adhesive material.

According to another exemplary embodiment of the present invention, amethod of determining a physical characteristic of a fillet of anadhesive material applied between elements of a semiconductor deviceusing structured light is provided. The method includes the steps of:(1) applying a structured light pattern to an adhesive fillet betweenelements of a semiconductor device; (2) creating an image of thestructured light pattern using a camera; and (3) analyzing the image ofthe structured light pattern to determine a physical characteristic ofthe adhesive fillet.

According to yet another exemplary embodiment of the present invention,a method of determining a flatness characteristic of a semiconductordevice using structured light is provided. The method includes: (1)creating an image of a structured light pattern reflected by a surfaceof a semiconductor device using a camera; and (2) analyzing the image ofthe structured light pattern to determine a flatness characteristic ofthe semiconductor device.

In accordance with certain exemplary embodiments of the presentinvention, these and other methods (including some or all of the stepsrecited herein) may be performed on a thermo-compression bondingmachine.

In accordance with certain exemplary embodiments of the presentinvention, the methods described herein (including methods ofdetermining a physical characteristic of an adhesive material on asemiconductor device element, methods of determining a physicalcharacteristic of a fillet of an adhesive material applied betweenelements of a semiconductor device, and methods of determining aflatness characteristic of a semiconductor device) may involve usingdifferent structured light patterns to achieve the best measurementresult (e.g., a physical characteristic or a flatness characteristic asdescribed herein). For example, the steps of creating an image of astructured light pattern using a camera, and analyzing the image of thestructured light pattern to determine a characteristic, may be repeated(thereby analyzing a plurality of images) to determine the desiredmeasurement result.

According to yet another exemplary embodiment of the present invention,a thermo-compression bonding system is provided. The thermo-compressionbonding system includes: (1) a support structure for supporting asemiconductor device element including an adhesive material; (2) astructured light source for providing a structured light pattern on theadhesive material; and (3) a camera for creating an image of thestructured light pattern on the adhesive material.

According to yet another exemplary embodiment of the present invention,a thermo-compression bonding system is provided. The thermo-compressionbonding system includes: (1) a support structure for supporting asemiconductor device; (2) a structured light source for providing astructured light pattern; and (3) a camera for indirectly viewing thestructured light pattern using a reflective surface of the semiconductordevice, the camera generating an image of the structured light pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawings. It is emphasizedthat, according to common practice, the various features of the drawingsare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawings are the following figures:

FIG. 1 is a block diagram view of elements of a thermo-compressionbonding machine in accordance with an exemplary embodiment of thepresent invention;

FIGS. 2A-2B are top views of an structured light patterns projected ontoan adhesive material in accordance with an exemplary embodiment of thepresent invention;

FIG. 3 is a three dimensional representation of an adhesive materialgenerated in accordance with an exemplary embodiment of the presentinvention;

FIG. 4A is a block diagram side view of an adhesive material fillet tobe imaged in accordance with an exemplary embodiment of the presentinvention;

FIG. 4B is a three dimensional representation of an adhesive materialfillet generated in accordance with an exemplary embodiment of thepresent invention;

FIG. 5 is a block diagram view of imaging elements, which may be used inconnection with a thermo-compression bonding machine, in accordance withan exemplary embodiment of the present invention;

FIG. 6 is a block diagram view of elements of a thermo-compressionbonding machine in accordance with an exemplary embodiment of thepresent invention;

FIGS. 7A-7C are a series of images of a structured light patternsreflected from surfaces of semiconductor devices in accordance with anexemplary embodiment of the present invention; and

FIG. 8 is another block diagram view of elements of a thermo-compressionbonding machine in accordance with an exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “structured light” is intended to be defined asis known to those skilled in the art, and specifically refers to lightincluding a projection (e.g., a pattern, such as pixels with differentgray levels in a grid or horizontal bar configuration) applied to asurface to be imaged.

In accordance with certain exemplary embodiments of the presentinvention, systems and methods for measuring (e.g., profiling,characterizing, etc.) elements of semiconductor devices using structuredlight are provided. Exemplary elements of semiconductor devices beingmeasured include adhesive material between elements of the semiconductordevice, a fillet of adhesive material between elements of thesemiconductor device, and semiconductor device surfaces.

Adhesive material elements measured may include, for example, curableliquid materials such as epoxy, non-conductive paste, etc. Such adhesivematerials may be applied between elements bonded together duringthermo-compression bonding. More specifically, a first element of asemiconductor device, with conductive regions, may be provided on asupport structure. An adhesive material may then be applied to thisfirst element. Then, a second element (which may be semiconductor die orother device including conductive pillars or the like) isthermo-compressively bonded to the first element. This bonding mayinclude, for example, heat and bond force. The adhesive material may bemeasured to determine, for example, a volume of the material (such as a3D volume of the material), a distribution of the material (e.g., thepattern of the material), etc.

Aspects of the present invention may also be used to measure a fillet ofadhesive material between such first and second elements. The fillet isthe portion of the adhesive material that is exposed between the twoelements (See, e.g., FIG. 4A). The fillet may be measured to determine,for example, a height of the fillet (reference number 410 in FIG. 4A), alength of the fillet (reference number 412 in FIG. 4A), a volume (e.g.,a 3D volume of the fillet), amongst other quantities.

Aspects of the present invention may also be used to measuresemiconductor device flatness characteristics. As will be appreciated bythose skilled in the art, it is typically desirable that semiconductordevices (e.g., semiconductor die to be thermo-compressively bonded toanother semiconductor element) are substantially flat and/or planar. Thepresent invention may be used to determine if such devices are within apredetermined flatness specification (e.g., tolerance).

Aspects of the present invention may also be used to measure forsemiconductor device crack characteristics including the size andlocation of such cracks.

As used herein, the term “semiconductor device” is intended to refer toany type of semiconductor device element including but not limited tobare semiconductor die, packaged semiconductor die, partially packagedsemiconductor die, a region of a substrate to which a die will bebonded, a semiconductor wafer (or a portion thereof) including aplurality of semiconductor die, etc. Elements of a semiconductor devicemay include a semiconductor die, a substrate for supporting asemiconductor die, etc.

FIG. 1 illustrates elements of a thermo-compression bonding machine 100.Many elements have been omitted from FIG. 1 (and other machinesillustrated herein) for clarity such as, for example, a bond headassembly, a material handling system, etc. Machine 100 includes astructured light source 102 (e.g., shown as, but not limited to, digitalfringe projector 102). Light source 102 includes grating 104 or otherstructure (such as a DLP chip in a digital fringe projector embodiment).Light 108 transmitted from source 102 is structured light that includesa structured light pattern imposed on the light, for example, usinggrate 104. FIG. 1 also illustrates support structure 110 which supportselement 112. Element 112 may be, for example, a semiconductor device towhich an adhesive material (e.g., an epoxy material, a non-conductivepaste, etc.—applied to the semiconductor device as a curable liquid) hasbeen applied. The adhesive material includes a diffusive surface 114.When structured light 108 is received by diffusive surface 114, at leasta portion of the resultant diffused light pattern 116 is imaged withinfield of view 120 of camera 118. The image generated by camera 118 maybe used to measure a physical characteristic of the adhesive material(included in elements 112, 114) such as a volume or volume distribution.While element 112 is described as an adhesive material, other types ofelements are contemplated such as substrates having a diffusive surface(or an at least partially diffusive surface).

FIGS. 2A-2B illustrate two top view images 216 a, 216 b of adhesivematerial samples as applied to respective semiconductor devices. Asillustrated, the adhesive material has a conventional “star” shaped or“burst” pattern. In FIG. 2A, the center portion 260 a of the adhesivematerial sample is not very clear. In FIG. 2B, the image had beenprocessed (e.g., using image processing hardware and/or software whichmay be included on a thermo-compression bonding machine) such that aclearer image is provided as in FIG. 2B. In FIG. 2B, the center portion260 b is much clearer than in FIG. 2A, and the structured light pattern(and the variation among the structured light lines in the pattern) ismore visible. Using such an image, image processing hardware and/orsoftware may be used to determine the desired physical characteristicwhich may be a simple characteristic (e.g., a number such as a volume)or a more complex physical characteristic such as a topographical map orrepresentation. FIG. 3 illustrates an example of such a map 360.

The exemplary structured light imaging approach illustrated in FIG. 1may be used to measure more than just a physical characteristic of anadhesive material such as shown in FIGS. 2A-2B. In another example, thelight may be used to image (and thereby measure) a physicalcharacteristic of an adhesive fillet. FIG. 4A illustrates a portion ofsemiconductor device 400 including a first semiconductor element 402(e.g., a die or substrate), an adhesive layer 404 disposed on element402, and a second semiconductor element 406 disposed on the adhesivelayer 406. Fillet 408 (which is part of adhesive material 404) extendspast an edge of element 406. It may be desirable to measure a physicalcharacteristic of fillet 408 for example, height 410, length 412, orcurvature “c”. It may be useful to know such a characteristic in orderto be confident that the adhesive material has not extended into areaswhere it should not extend. Of course, a more complex physicalcharacteristic such as a topographical map or representation may bemeasured. FIG. 4B illustrates an example of such a map.

The physical characteristic of a fillet measured according to thepresent invention may include measuring the characteristic around theentire perimeter along which the fillet extends. For example, if afillet extends around an entire edge of a semiconductor device, thisentire fillet may be measured.

In the images generated according to the present invention (e.g., usingcameras, structured light, etc.)—various imaging complications mayarise. One such complication relates to hot spots which may render theimage less clear. FIG. 5 illustrates a configuration that may be usefulto reduce such hot spots. More specifically, light source 576 (e.g., anLED or other source) is transmitted through polarizer 1, and intoprojection element 502 (e.g., including a grating or the like togenerate a structured light image). The structured light 508 is diffusedoff of test sample 578 (e.g., adhesive material on a semiconductordevice, etc.). A diffused image 520 is transmitted through polarizer 2and is received by camera 518. The use of polarizers may be useful inreducing the effect of hot spots.

Certain exemplary embodiments of the present invention may be used tomeasure other physical characteristics of semiconductor devices such asflatness characteristics, crack propagation, amongst others. FIG. 6illustrates an exemplary thermo-compression bonding machine 600 (withmany elements omitted for clarity) including a structured light source602 (e.g., shown as, but not limited to, digital fringe projector 102).Light source 602 includes grating 604 or other structure (such as a DLPchip in a digital fringe projector embodiment). Light 608 transmittedfrom source 602 is structured light that includes a structured lightpattern imposed on the light, for example, using grate 604. Structuredlight 608 is received by a diffuser screen 630 a. FIG. 6 alsoillustrates support structure 610 which supports element 612. Element612 may be, for example, a semiconductor device such as a semiconductordie or other element having a reflective (or at least partiallyreflective) upper surface 644. Camera 648 images an area within field ofview 640 including reflective surface 644 of element 612. Thisreflection allows camera to image the structured light pattern seen by(and possibly distorted by) element 612. As will be appreciated by thoseskilled in the art, this type of configuration allows for imaging of avirtual image as shown by reference number 630 b. As recited above, theimage generated by camera 648 may be used to measure a physicalcharacteristic of the element 612 such as a flatness characteristicand/or a crack propagation characteristic. FIG. 7A-7C are exemplaryimages of structured light distorted by various semiconductor devicesusing the technique illustrated in FIG. 6.

In certain exemplary embodiments of the present invention, it may bedesirable to image both a diffusive surface characteristic (e.g., anadhesive material characteristic) and a reflective surfacecharacteristic (e.g., a flatness characteristic). FIG. 8 illustrateselements of a thermo-compression bonding machine 800. Many elements havebeen omitted for clarity. Machine 800 includes a structured light source802 (e.g., shown as, but not limited to, digital fringe projector 802).Light source 802 includes grating 804 or other structure (such as a DLPchip in a digital fringe projector embodiment). Light 808 transmittedfrom source 802 is structured light that includes a structured lightpattern imposed on the light, for example, using grate 804. FIG. 8 alsoillustrates support structure 810 which supports element 812. Element812 may be, for example, a semiconductor device including a diffusivesurface 814 (e.g., an adhesive material) and a reflective surface 844(e.g., a die surface). Structured light 808 is received by switchingdiffusive screen 850 (illustrated as, but not limited to, a liquidcrystal diffuser screen). When it is desired to image the reflectivesurface 844, screen 850 may be operated in a diffusive mode, allowingcamera 848 to generate an image as described above with respect to FIG.6, and thereby allowing a physical characteristic (e.g., a flatnesscharacteristic, a crack propagation characteristic, etc.) to bemeasured. When it is desired to image diffusive surface 814, screen 850may be operated in a transparent mode, allowing camera 818 to generatean image as described above with respect to FIG. 1, and thereby allowinga physical characteristic (e.g., a volume, a volume distribution, etc.)to be measured.

Although the present invention has been described primarily with respectto imaging using structured lights, it is not limited thereto. Certainaspects of the present invention have applicability to use with otherforms and/or configurations of light.

Although the present invention has primarily been described inconnection with thermo-compressive bonding machines and processes (e.g.,thermo-compressively bonding a first semiconductor device element toanother semiconductor device element), it is not limited thereto. Forexample, the teaching of the present invention have application inconventional die attach systems and methods of using the same.

In certain exemplary embodiments of the present invention describedherein, closed loop processes (or feedback driven processes) aredescribed. For example, if a given physical characteristic (e.g.,adhesive material volume or distribution) is measured and is not withina predetermined specification (e.g., tolerance), then an aspect of thedispensing process (e.g., the volume of adhesive dispensed, the rate ofmaterial dispensed, the temperature of the material dispensed, amongstothers) may be adjusted in a closed loop manner. However, it is alsowithin the scope of the present invention to adjust other aspects of thethermo-compression bonding process to in order to achieve the desiredphysical characteristic specification. Such thermo-compression bondingprocess aspects that may be adjusted include, for example, bondingtemperature, bonding temperature profile, bond force, bonding time, etc.

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

What is claimed:
 1. A method of determining a physical characteristic ofan adhesive material on a semiconductor device element using structuredlight on a bonding machine, the method comprising the steps of: (a)dispensing an adhesive material on a semiconductor device elementconfigured to receive a second semiconductor device element through abonding process on the bonding machine, the second semiconductor deviceelement being configured to be bonded to the semiconductor deviceelement using a bond head assembly of the bonding machine, the secondsemiconductor device element including conductive pillars configured tobe bonded to conductive structures of the semiconductor device element,the adhesive material being configured to be provided between thesemiconductor device element and the second semiconductor deviceelement; (b) applying a structured light pattern to the adhesivematerial on the semiconductor device element using a light source of thebonding machine; (c) creating an image of the structured light patternusing a camera of the bonding machine; and (d) analyzing the image ofthe structured light pattern on the bonding machine to determine if aphysical characteristic of the adhesive material is within apredetermined specification.
 2. The method of claim 1 wherein theadhesive material is selected from the group consisting of an epoxymaterial, a non-conductive paste material, and a curable liquidmaterial.
 3. The method of claim 1 wherein the structured light patternincludes at least one of a parallel bar pattern and a grid pattern. 4.The method of claim 1 further comprising a step of adjusting an aspectof the step of dispensing the adhesive material for a subsequentsemiconductor device element if it is determined that the physicalcharacteristic is not within the predetermined specification at step(d).
 5. The method of claim 4 wherein the step of adjusting is performedusing a closed loop process whereby the adjusted aspect is determinedautomatically at least partially based on the determined physicalcharacteristic.
 6. The method of claim 1 wherein each of steps (a), (b),(c), and (d) are performed on a thermo-compression bonding machine. 7.The method of claim 1 wherein the physical characteristic includes atleast one of a volume of the adhesive material and a distribution of theadhesive material.
 8. A method of determining a physical characteristicof a fillet of an adhesive material applied between elements of asemiconductor device using structured light on a bonding machine, themethod comprising the steps of: (a) bonding a first element of asemiconductor device to a second element of the semiconductor deviceusing a bond head assembly on the bonding machine, the second elementincluding conductive pillars bonded to conductive structures of thefirst element during step (a), whereby an adhesive material is providedin an area between the first element and the second element; (b)applying a structured light pattern to an adhesive fillet of theadhesive material after step (a) using a light source of the bondingmachine; (c) creating an image of the structured light pattern using acamera of the bonding machine; and (d) analyzing the image of thestructured light pattern on the bonding machine to determine if aphysical characteristic of the adhesive fillet is within a predeterminedspecification.
 9. The method of claim 8 wherein the structured lightpattern includes at least one of a parallel bar pattern and a gridpattern.
 10. The method of claim 8 further comprising a step ofadjusting an aspect of a step of dispensing the adhesive material for asubsequent semiconductor device if it is determined that the physicalcharacteristic is not within the predetermined specification at step(d).
 11. The method of claim 10 wherein the step of adjusting isperformed using a closed loop process whereby the adjusted aspect isdetermined automatically at least partially based on the determinedphysical characteristic.
 12. The method of claim 8 wherein each of steps(a), (b), (c), and (d) are performed on a thermo-compression bondingmachine.
 13. The method of claim 8 wherein the physical characteristicincludes at least one of a height of the fillet and a length of theadhesive fillet.
 14. A method of determining a flatness characteristicof a semiconductor device using structured light on a bonding machine,the method comprising the steps of: (a) securing a semiconductor deviceusing at least one of a pick tool of a bonding machine and a place toolof the bonding machine; (b) creating an image of a structured lightpattern reflected by a surface of a semiconductor device using a cameraon the bonding machine while the semiconductor device is secured duringstep (a), the image being created using a light source of the bondingmachine; and (c) analyzing the image of the structured light pattern todetermine if a flatness characteristic of the semiconductor device iswithin a predetermined specification.
 15. The method of claim 14 whereinthe structured light pattern includes at least one of a parallel barpattern and a grid pattern.
 16. The method of claim 14 wherein each ofsteps (a), (b), and (c) are performed on a thermo-compression bondingmachine.
 17. The method of claim 14 wherein step (b)includes projectingthe structured light pattern from a light source onto a diffuser screen,the projected light pattern being reflected to the camera using thesurface of the semiconductor device.